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29
30// ---
31// Author: Craig Silverstein
32//
33// This verifies that GetPC works correctly.  This test uses a minimum
34// of Google infrastructure, to make it very easy to port to various
35// O/Ses and CPUs and test that GetPC is working.
36
37#include "config.h"
38#include "getpc.h"        // should be first to get the _GNU_SOURCE dfn
39#include <stdio.h>
40#include <stdlib.h>
41#include <signal.h>
42#include <sys/time.h>     // for setitimer
43
44// Needs to be volatile so compiler doesn't try to optimize it away
45static volatile void* getpc_retval = NULL;    // what GetPC returns
46static volatile bool prof_handler_called = false;
47
48static void prof_handler(int sig, siginfo_t*, void* signal_ucontext) {
49  if (!prof_handler_called)
50    getpc_retval = GetPC(*reinterpret_cast<ucontext_t*>(signal_ucontext));
51  prof_handler_called = true;  // only store the retval once
52}
53
54static void RoutineCallingTheSignal() {
55  struct sigaction sa;
56  sa.sa_sigaction = prof_handler;
57  sa.sa_flags = SA_RESTART | SA_SIGINFO;
58  sigemptyset(&sa.sa_mask);
59  if (sigaction(SIGPROF, &sa, NULL) != 0) {
60    perror("sigaction");
61    exit(1);
62  }
63
64  struct itimerval timer;
65  timer.it_interval.tv_sec = 0;
66  timer.it_interval.tv_usec = 1000;
67  timer.it_value = timer.it_interval;
68  setitimer(ITIMER_PROF, &timer, 0);
69
70  // Now we need to do some work for a while, that doesn't call any
71  // other functions, so we can be guaranteed that when the SIGPROF
72  // fires, we're the routine executing.
73  int r = 0;
74  for (int i = 0; !prof_handler_called; ++i) {
75    for (int j = 0; j < i; j++) {
76      r ^= i;
77      r <<= 1;
78      r ^= j;
79      r >>= 1;
80    }
81  }
82
83  // Now make sure the above loop doesn't get optimized out
84  srand(r);
85}
86
87// This is an upper bound of how many bytes the instructions for
88// RoutineCallingTheSignal might be.  There's probably a more
89// principled way to do this, but I don't know how portable it would be.
90// (The function is 372 bytes when compiled with -g on Mac OS X 10.4.
91// I can imagine it would be even bigger in 64-bit architectures.)
92const int kRoutineSize = 512 * sizeof(void*)/4;    // allow 1024 for 64-bit
93
94int main(int argc, char** argv) {
95  RoutineCallingTheSignal();
96
97  // Annoyingly, C++ disallows casting pointer-to-function to
98  // pointer-to-object, so we use a C-style cast instead.
99  char* expected = (char*)&RoutineCallingTheSignal;
100  char* actual = (char*)getpc_retval;
101
102  // For ia64, ppc64, and parisc64, the function pointer is actually
103  // a struct.  For instance, ia64's dl-fptr.h:
104  //   struct fdesc {          /* An FDESC is a function descriptor.  */
105  //      ElfW(Addr) ip;      /* code entry point */
106  //      ElfW(Addr) gp;      /* global pointer */
107  //   };
108  // We want the code entry point.
109#if defined(__ia64) || defined(__ppc64)     // NOTE: ppc64 is UNTESTED
110  expected = ((char**)expected)[0];         // this is "ip"
111#endif
112
113  if (actual < expected || actual > expected + kRoutineSize) {
114    printf("Test FAILED: actual PC: %p, expected PC: %p\n", actual, expected);
115    return 1;
116  } else {
117    printf("PASS\n");
118    return 0;
119  }
120}
121